Particles having a polymeric shell and their production

ABSTRACT

Particles have a hydrophilic core, for instance including an enzyme and a polymer, surrounded by a shell formed by interfacial condensation polymerisation in the presence of a polymeric stabiliser. Preferably the polymeric stabiliser is a random copolymer which will concentrate at the interface between oil and water and association by ionic interaction, condensation or otherwise is achieved between the stabiliser and one of the reactants before reaction with the other reactant. Dispersions of aqueous capsules in an aqueous medium are also disclosed.

This invention relates to condensation polymers and their production andin particular to membranes, especially capsule walls, formed of suchpolymers. In particular, the invention relates to the production ofparticles which have a core of core material encapsulated within apolymeric shell, including the production of such particles as asubstantially stable dispersion in a liquid.

Various methods are known for forming capsules having a shell coreconfiguration. One method involves coacervation of a polymer around thecore. Methods of forming a coacervate coating from a polymer solutionaround an aqueous core, and which are suitable for the manufacturer ofmicro capsules that can be included in a liquid detergent concentrate,are described in, for instance, the EP356239 and WO92/20771. It isdifficult to obtain by this technique a product in which the enzyme isretained satisfactorily in the particles while in the concentrate but isreliably released from the particles when the concentrate is dilutedinto wash water.

Another known method for making the shell of capsules having a shellcore configuration is interfacial polymerisation in which one or moremonomers polymerise at the interface between a dispersed phase and acontinuous phase to form a shell around the dispersed phase. Oneparticular type of interfacial polymerisation is interfacialcondensation (IFC) polymerisation. The polymer shell forms at theinterface between an oil phase and an aqueous phase as a result ofreaction between a water soluble IFC reactant (in the aqueous phase) andan oil soluble IFC reactant (in the oil phase).

IFC polymerisation has been applied for encapsulating a hydrophobic oroil core by forming an oil- in-water dispersion and causing IFCpolymerisation around each dispersed oil droplet. Methods for performingthis reaction have been developed to allow reasonably satisfactoryencapsulation. However these methods are of no value when the corematerial is aqueous or hydrophilic and, instead, it is then necessary toconduct the IFC polymerisation in a water-in-oil dispersion, i.e. in adispersion in which the aqueous or hydrophilic core material isdispersed in a continuous oil phase.

Although it is suggested in some patent examples, e.g., inJP-A-63-137996 that the water-in-oil process is satisfactorily operable,we have found that in practice it is not easy to obtain satisfactoryresults using environmentally acceptable materials. For instance thereis a risk that a substantial amount of the product may be a sediment ornot encapsulated, and the process may require the use of a halogenatedhydrocarbon. This may have good properties for the IFC polymerisationbut is now considered environmentally undesirable. The process can beparticularly difficult when it is desired to achieve a small particlesize (e.g. at least 90% by weight below 30 μm) and a product in whichsubstantially all the core material is enclosed within such particlesand the particles are substantially stably dispersed in a liquid.

It might be thought that the formation of a fine dispersion, i.e. anemulsion, would be promoted by the use of a water-in-oil emulsifier.However we have found that if we use a conventional water-in-oilemulsifier such as Span 85 (trade mark) it is difficult to obtain adispersion of satisfactory encapsulated particles in oil, especiallywhen the amount of dispersed phase is reasonably high. Increasing theamount or effectiveness of a conventional type of water-in-oilemulsification system does not improve the result. Instead, it seems totend to reduce satisfactory shell formation and to increase the risk ofnon-uniformity in the shell.

In EP-A-0671206, an IFC process is described for making the shell ofmicrocapsules having a size below 1 μm and is characterised by the useof a block copolymer as a protective colloid. A mixture of one of theIFC reactants with the core material is dispersed in a water immiscibleliquid and the other IFC reactant is dripped into this. In each of theexamples, the core material is a non-aqueous core based on polyethyleneglycol and the stabiliser is selected from polysiloxane polyalkyleneoxide block polymers, block polymers of lauryl methacrylate andpolyhydroxyethyl acrylate, together with a graft polymer of methylmethacrylate, cetyl methacrylate and an ethylene oxide adduct ofhydroxyethyl methacrylate. These stabiliser systems will be somewhatsimilar to water-in-oil emulsifiers because of their very pronouncedphysically separate hydrophilic moieties (i.e., the hydrophilic block)and hydrophobic moieties (i.e., the hydrophobic block). These systemstend to give unsatisfactory results when used in the manner described inEP 671206.

Accordingly there remains a need for IFC products and processes whichcan be conducted in convenient manner using convenient andenvironmentally acceptable materials to give a satisfactory wallstructure and a product of satisfactory and predetermined particle size.

According to the invention, we provide a particulate compositioncomprising particles having a hydrophilic core within a shell comprisinga membrane comprising an association product of (a) an IFC condensationproduct formed by reaction between a first IFC reactant having at leasttwo first condensation groups and a second IFC reactant having at leasttwo second condensation groups, and (b) an amphipathic polymericstabiliser which will concentrate at the interface between oil and waterand which has recurring hydrophobic groups and recurring reactivehydrophilic groups which associate with the second condensation groups.

The association may comprise a condensation reaction between thereactive hydrophilic groups and the second condensation groups. Forinstance when, as is preferred, the reactive hydrophilic groups comprisecarboxylic acid groups and the second condensation groups are amino, theassociation may involve the formation of an amide condensate linkagebetween the stabiliser and the IFC condensation product. This is thoughtto occur particularly when the stabiliser is a copolymer of anethylenically unsaturated carboxylic anhydride, such as maleicanhydride.

However the association can be any other type of association thatresults in attraction between the stabiliser and the second reactant(and thus also the IFC condensation product). The association oftencomprises ionic association, for instance as a result of the formationof an ionic salt between carboxylic groups and groups which will form asalt with them. For instance the polymeric stabiliser may havecarboxylic groups and a salt forming amine IFC reactant will then form asalt with them. It is then preferred that the amine should have beenintroduced in free base form, so as to minimise competition between thecarboxylic groups and other acid moieties in the reaction mixture.

Best results seem to be achieved when the polymeric stabiliser is acopolymer of ethylenically unsaturated polycarboxylic acid (includingdicarboxylic acid and the anhydrides) such as maleic acid or maleicanhydride, and the second reactant is a polyamine (including diamines,triamines and tetra amines) preferably having two to six carbon atomsbetween the amine groups. It appears that this configuration of adjacentcarboxylic groups and diamine or higher groups is particularly conduciveto the formation of strong association between the amine and thestabiliser, probably due to the formation of an internal, ring-formed,salt between the adjacent carboxylic groups and the diamine groups.

The invention also provides various processes for making particleshaving hydrophilic core within a shell formed by IFC polymerisation of asubstantially oil soluble first IFC reactant having at least two firstcondensation groups with a substantially water soluble second IFCreactant having at least two second condensation groups. These processesall comprise forming a water-in-oil emulsion of an aqueous corecomposition comprising core material and a second reactant in a waterimmiscible liquid which contains an oil soluble or oil swellablepolymeric stabiliser, blending the dispersion with the first IFCreactant and allowing reaction to occur between the first and second IFCreactants, thereby forming the shell.

In one preferred process, the polymeric stabiliser is an amphipathicpolymeric stabiliser having recurring hydrophobic groups and recurringreactive hydrophilic groups and the reactive hydrophilic groups areassociated (e.g., by condensation or by salt formation) with the secondcondensation groups of the second IFC reactant before the blending withthe first IFC reactant.

In another preferred process the polymeric stabiliser has pendantcarboxylic acid groups, the second IFC reactant is an amine, and thewater in oil dispersion is homogenised before blending with the firstIFC reactant. This homogenisation is beneficial because not only does itproduce the desired particle size for the final particles but also itallows some form of association to occur between the carboxylic andamine groups. For instance the homogenisation is conducted by stirringfor at least one minute, often three to ten minutes or more. Thetemperature can be ambient or elevated, for instance 40 to 80° C.

In another preferred process of the invention the polymeric stabiliseris a random copolymer formed by copolymerisation of a mixture ofethylenically unsaturated hydrophilic monomers and ethylenicallyunsaturated hydrophobic monomers.

In another process of the invention the blending of the dispersion withthe first IFC reactant is conducted by mixing the dispersion and thefirst reactant under conditions wherein the weight ratio of thedispersion to the second reactant remains substantially constant throughthe blending process.

In particular, the process is preferably conducted by in-line blendingof a feed containing the dispersion with a feed containing the firstreactant, since by this means it is easily possible to control the ratioof dispersion to first reactant so as to maintain it substantiallyconstant or at whatever other proportion is required.

In other preferred processes of the invention, the resultant dispersionof particles in water immiscible liquid is treated by adding a watermiscible organic liquid (preferably a surfactant) to the dispersion anddistilling off the water immiscible liquid, thereby forming a dispersionof the particles in the water miscible organic liquid. If desired, thedispersion in water immiscible liquid and/or water miscible liquid maybe subjected to distillation so as to render it substantially anhydrous.

The processes of the invention, and especially those utilising apolymeric stabiliser that associates in some manner with the secondreactant before the reaction between the first and second reactants,allow the production of more uniform particles at satisfactoryconcentrations and in particular it allows the production asubstantially stable dispersion of small encapsulated particles (atleast 90% by weight below 30 μm). They can beneficially influence theproduction of the IFC shell. For instance the amount of either or bothof the reactants required to obtain a shell of defined properties can bereduced by optimising the polymeric stabiliser and its amount. Furtherthe particles made using the stabiliser can be dispersed stably intoanother liquid (for instance a liquid detergent concentrate) more easilythan if the polymeric stabiliser is not used.

The processes of the invention may comprise the subsequent step ofdistilling off most or all of the water from the aqueous corecomposition until the particles comprise a substantially anhydrous coreencapsulated within the IFC polymer shell. The distillation is oftenreferred to as azeotropic distillation as some of the organic liquid isusually distilled off with the water.

In another aspect of the invention, other articles comprising a membranecan be formed. Thus an interface can be formed between an aqueous phaseand an oil phase, such as a flat interface to form a flat film or atubular interface to form a tube, and the membrane which is formed atthis interface can be an association product of the IFC condensationproduct and the amphipathic polymeric stabiliser. Although the inventioncan be applied to the production of films in this manner, forconvenience all further description is in the context of the productionof particles.

The invention can be applied to the production of relatively coarseparticles, for instance at least 90% by weight above 50 μm and typicallyabove 100 μm with generally 90% by weight being below 1000 μm and oftenbelow 500 μm. These beads can be separated from the dispersion as drybeads.

Preferably, the invention is applied to the production of finerparticles, generally with at least 90% by weight of the particles havinga dry size below 30 μm. The invention not only permits the production ofa relatively high concentration (for instance 25 to 50% by weight of thefinal product) of such particles but it also permits the production ofthese particles in substantially individual form and substantiallystably dispersed in the water immiscible liquid.

By referring to the dry size of the particles we mean the size of theparticles measured after the dispersion has been distilled so as toprovide a substantially anhydrous core, for instance having a totalwater content (based on the total weight of the particles) of below 20%and usually below 10% by weight. However if, in any particular process,it is not possible to dry the dispersion then the dry size can beestimated from measurement of the wet size of the particles coupled withan estimation of the extent to which the particles would shrink if theywere dried.

By saying that the particles are substantially individually and stablydispersed in the water immiscible liquid we mean that the total numberof particles (including agglomerated particles) above 30 μm is below 10%by weight and that preferably no settlement of particles occurs but ifany does occur then the settled particles can very easily be redispersedby gentle stirring. Preferably the particles have a dry size at least80% (and preferably at least 90%) by weight below 15 μm or 20 μm and soagain the number of agglomerates having a size greater than 15 μm or 20μm should be low. Preferably the dry size is at least 70% (andpreferably 80% or 90%) by weight below 10 μm. The particles can be assmall as, for instance, 50% below 1 μm but preferably at least 50% andmost preferably at least 70% by weight and have a size in the range 1-5μm.

Another way of defining the size is that the mean particle size (on aweight average basis) is preferably below 20 μm and most preferablybelow 10 μm often in the range of 1-5 μm.

The particles have to be made initially as a water-in-oil dispersion ina water immiscible liquid. This liquid is preferably free of halogenatedhydrocarbons (such as chloroform) and is preferably a hydrocarbon.

The resultant dispersion, optionally after distillation to render thecore substantially anhydrous, can be supplied to the user as such, forinstance for incorporation into a detergent concentrate. Often, however,it is preferred to exchange the water-immiscible liquid in which thedispersion is formed for a different organic liquid which can be anotherwater-immiscible liquid but is usually a surfactant or a water miscibleliquid and may contain some water. However it is often convenient forthe amount of water in this liquid to be kept relatively low, forinstance below 20% weight, so that the final composition will then be adispersion in a substantially non-aqueous liquid.

A suitable method of achieving this change in the liquid is by a methodsuch as is described in WO 94/25560. The method comprises forming theinitial IFC dispersion in water-immiscible liquid, optionallydehydrating the dispersed particles by azeotropic distillation of thedispersion and adding to the dispersion a liquid selected fromwater-immiscible liquids and, preferably, surfactants and water-miscibleliquids and which is less volatile than the initial water immiscibleliquid, and distilling the initial water-immiscible liquid off from thedispersion until the amount of the initial water-immiscible liquidremaining in the dispersion is below 20% by weight of the liquid phasein the dispersion.

Although the dispersion is often dehydrated (before, during or afteradding the surfactant or other liquid), removal of water is notessential since the water may often satisfactorily equilibrate with thecontinuous phase. This discovery is useful in the present invention butis also applicable to processes as described in WO 94/25560.

The added liquid may be a water-miscible and organic liquid, and it canbe aqueous. For instance it may be a material such as a glycol, butpreferably it is a surfactant, generally a non-ionic surfactant, withthe result that the final product is a dispersion of the particles inthe surfactant. The amount of the particles in the surfactant or otherdispersion will normally be above 5% or 10% dry weight and usually willbe above 20% or more. The dispersion may be fluid or meltable, i.e. thenon-aqueous liquid may be a wax when cool and may have to be heated inorder to provide a liquid state. Reference should be made to WO94/25560for a full description of suitable materials and process conditions.

The invention therefore also provides a novel composition comprising adispersion in an aqueous liquid (e.g., an aqueous surfactant) ofparticles having an aqueous core within a polymeric shell. This may beformed by any suitable IFC or other shell-forming method preferably byIFC using polymeric stabiliser as decribed herein.

The processes of the invention can yield dispersions in a substantiallynon-aqueous liquid or an aqueous liquid of particles having a dry sizeof at least 90% by weight below 30 μm wherein the particles aresubstantially individually and stably dispersed in the liquid (or wax)and wherein the particles have a core surrounded by a shell formed of acondensation polymer wherein the dispersion is stabilised by anoil-soluble or oil-swellable amphipathic polymeric stabiliser. When theliquid is a meltable wax, rather than a true liquid at room temperature,the dispersion will be a meltable solid at room temperature. The corecan include a polymeric matrix and usually includes an activeingredient, such as an enzyme.

The compositions obtained in the invention can be used in any suitablemanner. For instance, when the active ingredient is a detergent enzymeor other detergency material the dispersion in oil, surfactant or otherliquid may be dispersed into a detergent liquid concentrate as describedin application . . . filed even date herewith reference PRL03621WO andclaiming priority from inter alia, GB 9526706.8 of Dec. 29th 1995.

When carrying out the initial manufacture of the particles having anaqueous core, an aqueous composition which is to provide the corematerial is dispersed into a water-immiscible non-aqueous liquid. Asubstantially water-soluble IFC reactant having low or no oil solubilityis included in the dispersion. In some cases, certain components (egsome IFC reactant or a pH adjusting agent) to be incorporated in theshell or core of the particles may be introduced before, during or afterencapsulation. If desired, the substantially water-soluble reactant ismixed into the aqueous core composition before that is dispersed in thewater-immiscible liquid, but if desired the reactant and, optionally,other appropriate components (eg a pH adjusting agent such assodium-hydroxide) can be mixed into a pre-formed dispersion of theaqueous composition in the water-immiscible liquid. In some instances,the IFC reactant can be water in the aqueous core composition. In someinstances shell formation may be formed by two or more sequentialreactions.

It is generally preferred that the water soluble reactant should havesufficient solubility in the oil phase that a small proportion of itwill dissolve in the oil phase or that it will, at least, migrate to theinterface between the oil and water phases. This promotes the desiredassociation between the stabiliser and the substantially water solublereactant.

The polymeric stabiliser should be included in the oil phase before IFCpolymerisation occurs and in practice it is usually preferred for thestabiliser to be added to the water-immiscible liquid before dispersingthe aqueous core composition into it, although if desired some or all ofthe stabiliser can be added with or after the aqueous core composition.Generally the stabiliser is supplied as a solution of swollen ordissolved stabiliser in an oil which becomes part of the totalwater-immiscible liquid.

If the oil-soluble IFC reactant is substantially unreactive under theconditions prevailing during the formation of the initial dispersionthen the reactant can also be included in the water-immiscible liquidbefore or during the formation of the dispersion of aqueous corecomposition in the water-immiscible liquid. Usually it is preferred toform the aqueous dispersion of aqueous core composition andwater-soluble IFC reactant in water-immiscible liquid which contains theamphipathic polymeric stabiliser, and then mix the oil-soluble IFCreactant into the dispersion. The oil soluble IFC reactant is usuallynot added until there has been adequate time (usually at least 2minutes, e.g., 3 to 20 minutes) for association to occur between thestabiliser and the other IFC reactant. Generally homogenisation or othermixing is applied to promote association.

The formation of the dispersion will be conducted with whatever level ofhomogenisation is required in order to achieve the desired particlesize. Thus if relatively coarse particles are required simple agitationmay be sufficient but if a fine particle size is required then one ormore passes through a Silverson or other homogeniser may be required.

Reaction between the water-soluble and oil-soluble IFC reactants is thenallowed to occur. The oil soluble reactant has low or no solubility inwater. Depending upon the combination of reactants, this may occurrelatively spontaneously at the mixing temperature or, more usually,reaction is promoted by warming the entire dispersion, for instance to atemperature in the range of 30° C.-90° C. It may be desirable to warm orcool the dispersion to a suitable reaction temperature prior to addingthe oil soluble reactant and/or to warm or cool the reactant (oftendissolved in solvent) prior to addition to the dispersion. Theoil-soluble reactant can be added in neat form but, in order tofacilitate mixing of the oil soluble reactant into the pre-formeddispersion, the reactant is preferably added as a solution in anappropriate, e.g. organic, solvent. The solvent becomes part of thewater-immiscible liquid phase of the dispersion.

It is generally desirable to stir the dispersion while the reactionoccurs. Although the reaction may appear to be substantially completequite quickly, for instance within five minutes from adding theoil-soluble IFC reactant, it is generally desirable to continue thestirring at the chosen reaction temperature for at least ten minutes upto an hour or more, typically around half an hour, to give maximumopportunity for full reaction to occur. Stirring may then bediscontinued and the resultant composition either used as such or, moreusually, subjected to dehydration and, preferably, solvent exchange bythe general methods described above.

By referring to a water-soluble IFC reactant we mean a reactant whichdissolves in the aqueous core composition (or water when this is thereactant). By referring to an oil-soluble IFC reactant and oil-solubleamphipathic polymeric stabiliser we mean a reactant or stabiliser whichdissolves in the water-immiscible liquid. Accordingly the water-solubleIFC reactant will partition into the aqueous phase and the oil-solubleIFC reactant and the polymeric stabiliser will partition into thewater-immiscible liquid with a significant partition coefficient,usually at least 5 and generally above 10. The polymeric stabiliser neednot be truly soluble in the water-immiscible liquid (provided it is muchless soluble in water) but may instead be in the form of a colloidal orother dispersion and so may be described as oil-swellable rather thanoil-soluble.

The water-immiscible liquid can consist of a single non-aqueous liquidor can be a blend of two or more non-aqueous liquids. It should be waterimmiscible so as to minimise migration of the aqueous core compositionand the water-soluble IFC reactant into the oil phase. It may be anyenvironmentally acceptable water-immiscible liquid which has convenientvolatility and other properties for the formation of the dispersion andfor its eventual removal by distillation (if appropriate). Preferably itis a hydrocarbon, preferably a relatively low boiling and thereforevolatile, aliphatic hydrocarbon. It is normally a paraffinichydrocarbon.

The polymeric stabiliser is preferably amphipathic, by which we meanthat it includes recurring hydrophilic and hydrophobic monomer units.

The polymer may be a condensation polymer, in which event it is normallya condensate of an oil soluble polymer with a water soluble polymer. Theoil soluble polymer is often a polyester carboxylic acid and the watersoluble polymer may be a polyethylene glycol or other polyhydroxycompound, for instance as described in GB-A-2,002,400 and thus thepolymer may be a condensate of polyethylene glycol with hydroxy stearicacid. A preferred condensation polymer, which already contains someamino groups, is formed when the water soluble polymer is a polyamine,for instance as described in EP-A-333,501. Thus the condensation polymermay be a condensate of hydroxy stearic acid and polyethylene imine.Block copolymers for use in IFC processes are described in EP-A-671206but are not as useful as ionic polymers, especially ionic randompolymers.

Therefore it is generally preferred for the polymer to be a randomcopolymer of at least one ionic, and therefore hydrophilic,ethylenically unsaturated monomer with at least one water insoluble,non-ionic and therefore hydrophobic ethylenically unsaturated polymer.By referring to the polymer as random we merely mean that it is made bycopolymerisation of a blend of the monomers.

The amphipathic polymeric stabiliser is preferably ionic. It can beamphoteric or cationic but preferably is anionic and thus us preferablya co-polymer of at least one anionic monomer with at least onewater-insoluble non-ionic monomer. The molar amount of the ionic monomeris generally in the range 1 to 50% (often 10 to 30%) based on the totalmolar amount of ionic and water insoluble non-ionic monomers.

The use of dicarboxylic acid components in the stabiliser appears, asindicated above, to promote association between the stabiliser and theIFC condensate. In order to promote this association, the carboxylicgroups are generally present in free acid form, so as to facilitate theformation of internal salts. However in other instances appropriateassociation, such as condensation, can be achieved when the carboxylicacid groups are present as short-chain alkyl esters of ethylenicallyunsaturated carboxylic acid groups, such as C1-4 low alkyl (meth)acrylate groups.

In general suitable stabilisers are addition copolymers containing bothhydrophobic and hydrophilic moieties in such a ratio as to reside at theinterface between the oil and water phase. The desired pendant groupsare usually introduced by choice of monomers, but (less preferably)pendant groups in the final stabiliser can be provided by condensationor other reaction on to the stabiliser before it is used in theinvention.

The water-insoluble non-ionic monomers should have a partitioncoefficient K between hexane and deionised water at 20° C. of at least 5and preferably at least 10. Suitable hydrophobic monomers include higheralkyl esters of α, β-ethylenically unsaturated carboxylic acids such asdodecyl acrylate, dodecyl methacrylate, tridecyl acrylate, tridecylmethacrylate, tetradecyl methacrylate, octadecyl acrylate, Octadecylmethacrylate, ethyl half esters of maleic anhydride, diethyl maleate,and other alkyl esters derived from the reaction of alkanol having 4 to20, preferably 8 to 20, carbon atoms, with ethylenically unsaturatedcarboxylic acid such as acrylic acid, methacrylic acid, fumaric acid,itaconic acid and acconitic acid. Other suitable hydrophobic monomersinclude styrene, alkyl styrenes such as methyl styrene, vinyl estersincluding vinyl acetate, vinyl halides, acrylonitrile,methacrylonitrile, ethylene, butylene, butadiene and other olefines andallyl ethers of non-ionic ethoxylated surfactants.

Suitable hydrophilic moieties include all water soluble ethylenicallyunsaturated monomers that undergo addition polymerisation, such asacrylic acid, methacrylic acid, acrylamide, 2-acrylamide-2-methylpropane sulphonic acid, itaconic acid, maleic acid, fumaric acid;ethylenically unsaturated quaternary compounds such as dimethyl aminoethyl acrylate or methacrylate quaternised with methyl chloride, diallyldimethyl ammonium chloride vinyl or allyl sulphonates, vinyl or allylamines, hydroxy lower-alkyl esters of ethylenically unsaturated acids,and other alkylaminoalkyl—(meth) acrylates and—(meth) acrylamides.

It is particularly desirable to use a polycarboxylic acid, especially adi-carboxylic acid such as maleic acid (utilised either as the acid orthe anhydride) or itaconic acid as part or all of the acid component(for instance at least 20% by weight of the acid, often at least 50%).

Other ethylenically unsaturated comonomers may also be included, so asto modify the solubility parameters of the stabilisers to promoteprecipitation and residence at the interface between the oil and waterphase.

Suitable monomers are short chain alkyl esters of ethylenicallyunsaturated carboxylic acids such as acrylic acid, methacrylic acid,fumaric acid, itaconic acid and aconitic acid, where the alkyl groupgenerally contains between 1 and 4 carbon atoms e.g. methyl acrylate ormethacrylate, butyl acrylate or methacrylate.

Ratios of hydrophobic to hydrophilic monomer can be between 90 parts byweight of hydrophobic monomer and 10 parts by weight of hydrophilicmonomer to 20 parts by weight of hydrophobic monomer and 80 parts byweight of hydrophilic monomer.

When the short chain esters are incorporated they replace thehydrophobic monomer in the copolymer, and the dry weight ratio of shortchain ester will not exceed 50 parts. Minor amounts of othernon-interfering monomers can be included such as difunctional or otherpolyfunctional monomers.

The optimum monomer blend, and thus the optimum stabiliser in anyparticular process, will depend inter alia on the choice of waterimmiscible liquid and the core material and the IFC reactants and theproportions of each of these.

The stabiliser usually has a molecular weight (measured by gelpermeation chromatography of above 2000 and preferably above 10,000 upto, for instance 100,000 or 200,000.

The selection of a suitable blend and molecular weight can be done byperforming the IFC polymerisation in a water-in-oil emulsion andsubjecting the product to microscopic examination. Additionally, asimple test to facilitate selection of aqueous and oil phases is asfollows.

The aqueous phase containing the water soluble IFC reactant is spread asa layer in a vessel. The oil phase is spread over it with minimumintermixing at the chosen reaction temperature, the oil phase containingthe chosen amount of IFC reactant. It will be found that the quality ofthe film which is formed at the interface varies according to thecontent of the two phases, for instance any polymeric stabiliser and itsamount. Once a combination of phases has been found that can give both asatisfactory water-in-oil dispersion and a film in the test describedabove, it is predictable that reasonable wall formation will occur.Combinations of materials for use in the second aspect of the inventioncan be selected in this manner.

The test is preferably used to optimise the stabiliser. Accordingly oncea monomer concentration and stabiliser concentration has been foundwhich gives a reasonable film, the stabiliser and its amount can bevaried in successive tests and the effect on film quality observed.

When the stabiliser is replaced by, or supplemented by a significantamount of a conventional non-polymeric water-in-oil emulsifier then filmquality may deteriorate significantly and a coherent film may not beobtained. The reason for this is not clear but it seems that theemulsifier may promote emulsification of the phases and promoteprecipitation polymerisation within the oil phase due to hydrophilicmicelle formation within the oil phase, whereas the stabiliser maypromote emulsification of the phases and concentration of thepolymerisation at the interface.

The polymerisation is preferably conducted in the substantial absence(e.g., below 3%, preferably below 1% and preferably zero or near zero)of non-polymeric water-in-oil emulsifier or any other material whichinterfere with satisfactory performance of the process.

The IFC reactants are chosen so as to give the desired condensatepolymer. It is particularly preferred for the condensate to be apolyamide but other condensates which can be formed in the invention arepolyesters, polyurethanes, polyureas and epoxies. The use of polyamideis particularly useful in capsules for detergents. When the condensateis a polyamide, it is best obtained by reaction of a diamine (or higheramine) with a dicarboxylic acid (or higher carboxylic acid) usually as aderivative such as the acid halide or anhydride. The amine is preferablythe substantially water soluble IFC reactant and can be one or variousaliphatic polyamines such as ethylene diamine, hexamethylene diamine,hexane diamine, diethylene tetramine, ethylene tetramine, diaminobenzene, piperazine, tetramethylene pentamine or, preferably, diethylenetriamine.

The acid component is preferably the oil soluble IFC reactant and can bein the form of an acid halide. It can be, for instance, adipyl, sebacylor phthalyl chloride or dodecanedioc acid chloride but is preferablyterephthaloyl chloride.

It should be noted that the water soluble reactant can have somesolubility in the oil phase such that it can react with the oil solubleamphipathic polymeric stabiliser in the oil phase. For instance the freebase amines are preferred and will generally have some solubility in theoil phase.

When the condensate polymer is a polyester it can be formed by reactionbetween, for instance, any of the acids or acid derivatives mentionedabove as the oil soluble IFC together with a water soluble polyol suchas ethylene glycol, butane diol, polycaprolactone diol or Bisphenol A.

When the condensate polymer is a polyurethane it can be formed byreaction between a suitable hydroxy or amine compound selected from anythose discussed above as the water soluble IFC reactant and an oilsoluble isocyanate reactant such as toluene di-isocyanate or othersuitable material such a hexamethylenebis chloroformate.

Another type of polyurethane can be obtained by using an oil-solubleoligomeric isocyanate. This reacts with water at the interface toproduce amino groups which react with isocyanate groups in the oil phaseto form an IFC film at the interface.

When the condensate polymer is an epoxy, it can be made by reactionbetween, for instance, ethylene diamine or other water soluble amine orhydroxy compound with an epoxy resin as the oil soluble IFC reactant.

The process of the invention preferably comprises forming a water-in-oildispersion of the aqueous core phase in water immiscible liquidcontaining the polymer as a stabiliser and which is free of the firstcondensation groups, reacting the polymer with non-polymeric firstreactant which has sufficient solubility in the water immiscible liquidto react with the polymer, and then dispersing the second, oil soluble,IFC reactant into the dispersion and allowing condensation to occur. Thereaction may occur relatively spontaneously at the mixing temperatureor, more usually, reaction is promoted by warming the entire dispersion,for instance to a temperature in the range of 30° C.-90° C. It may bedesirable to warm or cool the dispersion to a suitable reactiontemperature prior to adding the oil soluble reactant and/or to warm orcool the reactant (often dissolved in solvent) prior to addition to thedispersion. The oil-soluble reactant can be added in neat form but, inorder to facilitate mixing of the oil soluble reactant into thepre-formed dispersion, the reactant is preferably added as a solution inan appropriate, e.g. organic, solvent. The solvent becomes part of thewater-immiscible liquid phase of the dispersion.

It is generally desirable to stir the dispersion while the reactionoccurs. Although the reaction may appear to be substantially completequite quickly, for instance within five minutes from adding theoil-soluble, second, IFC reactant, it is generally desirable to continuethe stirring at the chosen reaction temperature for at least ten minutesup to an hour or more, typically around half an hour, to give maximumopportunity for full reaction to occur. Stirring may then bediscontinued and the resultant composition either used as such or, moreusually, subjected to dehydration and, preferably, solvent exchange bythe general methods described above.

Although the process can be conducted by adding the second reactant tothe dispersion, preferably the process is conducted by mixing thedispersion and the second reactant under conditions such that the weightratio of dispersion to second reactant is substantially constantthroughout the mixing process, for instance so that it does not vary bymore than a factor of about 1.5 or 2 during the process. Preferably theprocess is conducted by in-line mixing of two feeds, one containing thedispersion and the other containing the second reactant. By this means,the ratio of second reactant to first reactant can be maintainedsubstantially constant throughout the process and therefore the degreeof reaction between the second reactant and the first condensationgroups in the dispersion can be maintained more uniform.

The material which is to form the core of the capsules is usuallyhydrophilic and is usually introduced into the process as an aqueouscomposition. It can consist solely of an aqueous solution or dispersionof an active ingredient which is to be trapped within the capsules. Forinstance the core material may include any active ingredient which willpartition preferentially into the aqueous phase in the process. Theactive ingredient should preferably have a high molecular weight inorderto minimise the risk of migration through the shell. For instance it maybe in the form of a crystal or complex of large molecular size. Theactive ingredient can be, for instance, an agriculturally useful activeingredient such as an herbicide or pesticide, a pharmaceutically usefulactive ingredient, a fragrance, or a biologically active material suchas an enzyme. Other suitable active ingredients include opticalbrighteners, photo bleaches, proteins, a substrate for an enzyme or anenzyme stabiliser. Combinations of such ingredients, e.g. an enzyme anda stabiliser therefor, may be appropriate.

Inks (including various dye or pigment compositions) and chemicallyreactive materials which need to be kept isolated from other materialsprior to rupture or other release mechanism may be used as the activeingredient.

Preferred active ingredients include enzymes. An enzyme may beintroduced, for example, in the form of a purified enzyme or an extract(such as a fermentation broth) containign cell debris and/or otherby-products from the initial production of the enzyme. Very suitableenzymes include enzymes of types which may be usefully included in adeteregent, as well as enzymes of types employed in industrial processes(e.g., in the starch-processing industry, in textile treatment or in theprotein industry).

Enzymes of relevance in the context of the present invention include,but are by no means limited to, the following [enzyme classificationnumbers (EC numbers) referred to herein being in accordance with theRecommendations (1992) of the Nomenclature Committee of theInternational Unionof Biochemistry and Molecular Biology, Academic PressInc., 1992].

Proteases (i.e., peptidases, EC 3.4), such as proteases obtainable fromanimals, plants or—in particular—microorganisms (notably bacterial orfungi), as well as mutants of such proteases produced by chemicalmodification or genetic engineering. Suitable commercially availableproteases include Alcalase™, Savinase™, Everlase™, Durazym˜, Esperase™and Flavourzyme™ (all available from Novo Nordisk A/S, Denmark)Maxatase™ Maxacal™, Maxapem™ and Properase™ (available fromGist-Brocades), Purafect™ and Purafect™ OXP (available from GenencorInternational), as well as Opticlean™ and Optimase™ (available fromSolvay Enzymes).

Lipases (e.g., triacylglycerol lipases, EC 3.1.1.3), such as lipasesobtainable from animals (e.g., mammals), plants or—inparticular—microorganisms (notably bacteria or fungi), as well asmutants of such lipases produced by chemical modification or geneticengineering. Lipases of types referred to in the literature as“cutinases” (such those obtainable from Pseudomonas mendocina asdescribed in WO88/09367, or from Fusarium solani f. pisi as described,e.g., in WO90/09446) are included in this connection. Suitablecommercially available lipases include Lipolase™ and Lipolase Ultra™(available from Novo Nordisk A/S, Denmark), Lipomax™, Lumafast™ and M1Lipase™ (available from Genencor International), and Lipase P “Amano”(available from Amano Pharmaceutical Co.Ltd.).

Amylases [e.g., α-amylases, EC 3.2.1.1, β-amylases, EC 3.2.1.2, andamyloglucosidases (glucoamylases), EC 3.2.1.3], such as amylasesobtainable from microorganisms (notably bacteria or fungi), as well asmutants of such amylases produced by chemical modification or geneticengineering. Suitable commercially available amylases include Termamyl™,BAN™, Duramyl™, Fungamyl™ and AMG™ (all available from Novo Nordisk A/S,Denmark), as well as Rapidase™ and Maxamyl™ P (available from GenencorInternational).

Cellulases (e.g., endo-1,4-β-glucanases, EC 3.2.1.4), such as cellulasesobtainable from microorganisms (notably bacteria or fungi), as well asmutants of such cellulases produced by chemical modificatin or geneticengineering. Suitable commercially available cellulases includeCelluzyme™, Celluclast™, Cellusoft™ and Denimax™ (all available fromNovo Nordisk A/S, Denmark), and KAC-500(B)™ (available from KaoCorporation).

Oxidoreductases [EC 1; including phenol-oxidases such as laccases (EC1.10.3.2) and other enzymes classified under EC 1.10.3; and peroxidases(EC 1.11.1), notably those classified under EC 1.11.1.7], such asoxidoreductases obtainable from plants or microorganisms (notablybacteria or fungi), as well as mutants of such oxidoreductases producedby chemical modification or genetic engineering. Suitable laccasesinclude those obtainable from fungal species within genera such asAspergillus, Neurospora, Podospora, Botrytis, Collybia, Fomes, Lentinus,Pleurotus, Trametes, Polyporus, Rhizoctonia, Coprinus,Psatyrella,Myceliophthora, Schytalidium, Phlebia, Coriolus, Pyriculariaor Rigidoporus, such as laccase obtainable from Trametes villosa (alsopreviously known, inter alia, as Polyporus pinsitus) or fromMyceliophthora thermophila. Suitable peroxidases include plant-derivedperoxidases, such as horseradish peroxidase or soy bean peroxidase, aswell as peroxidases obtainable from fungal species within genera such asFusarium, Humicola, Trichoderma, Myrothecium, Verticillium, Arthromyces,Caldariomyces, Ulocladium, Embellizopus or Mucor, or from bacterialspecies within genera such as Streptomyces, Streptoverticillium,Bacillus, Rhodobacter, Rhodomonas, Streptococcus, Pseudomonas orMyxococcus. Other sources of potentially useful peroxidases are listedin B. C. Saunders et al, Peroxidase, London 1964, pp. 41-43.Particularly useful peroxidases include those obtainable from Coprinusspecies such as C. cinereus or C. macrorhizus (as described, e.g., inWO92/16634).

Other relevant types of enzymes within the context of the inventioninclude xylose isomerases (EC 5.3.1.5) useful, e.g., in the conversionof D-glucose to D-fructose (e.g., in the manufacture of fructose syrupsin the starch-processing industry).

As mentioned above, a stabiliser for the enzyme may be included in thecore.

The aqueous core composition preferably also includes an aqueoussolution or emulsion of polymeric or polymerisable material which canform a polymer matrix. The active ingredient is preferably distributedsubstantially uniformly throughout the aqueous composition as adispersion or solution, but may be distributed non-uniformly.

The polymer may be introduced as an emulsion of water insoluble polymeror it may be introduced in the form of a soluble derivative which isinsolubilised during subsequent dehydration, for instance as describedin EP 356239 or WO 92/20771 or GB 9526668.0. It can be a copolymer of ahydrophobic monomer with a free acid or free base form of an ionicmonomer which is introduced as a water soluble salt. For instance it maybe a copolymer with a free base amino monomer introduced as a salt withacetic acid or other salt, which is then volatilised to give aninsoluble copolymer. Alternatively it may be introduced as a watersoluble polymer and remain water soluble throughout any subsequentdrying procedure. Polymerisation or cross linking may occur, forinstance during subsequent drying, using any suitable polymerisation orcross linking reaction mechanism.

Potentially soluble polymers that can be included in this manner includematerials such a polyvinyl pyrrolidone, polyacrylic acid (generally assodium or other salt) polyacrylamide or a calcium-independent suphonatepolymer. Natural or modified natural polymers such as gums orcarbohydrates can be used.

The polymer is preferably a polymer which will cause release of theactive ingredient by co-operating with water which migrates by osmosisthrough the shell from wash water to expand and stretch the shell, asdescribed in our application Ser. No. 08/875,052 reference PRL03621WOfiled even date herewith claiming priority from GB 9526706.8 filed 29thDec. 29th 1995.

The proportions of the IFC reactants, and the total weight of thepolymer shell, can be selected according to the desired properties ofthe shell. Generally the shell provides from 2%-50%, often around10%-30% by weight of the total dry weight of the encapsulated material(i.e. shell and dehydrated core) but not usually more than about 50% or60%. The molar proportions of the water soluble and oil soluble IFCreactants are generally in the range 10:1 to 1:10. For instance themolar ratio of water-soluble reactant: oil-soluble reactant may be from10:1 to 1:3, often from 5:1 to 1:1.

The amount of polymeric stabiliser is generally in the range 0.1 to 10%usually around 0.5%-3%, by weight stabiliser based on the total weightof the dispersion in which the particles are formed. The amount based onthe dry weight of the particles is generally in the range 0.5 to 30%,often around 3%-10% by weight.

The amount of aqueous core composition and water soluble IFC reactant isusually at least 5 or 10% by weight, preferably at least 25% by weightof the aqueous dispersion but it is usually not more than 60% or 70%.

The dry weight of the core in the aqueous dispersion is usually at least2% or 5% by weight and preferably at least 10%. Often it is not above40% or 50% by weight.

The particles can be caused to release active ingredient from their coreinto any desired location by release techniques such as physical ruptureby compression or otherwise, or by expansion of swellable materialwithin the core to stretch or rupture the shell so as to allowpermeation through the shell.

Preferably the capsules are utilised for encapsulating enzyme which isreleased by osmotic pressures, the capsules being incorporated in aliquid detergent concentrate as described in our application no Ser. No.08/875,052 claiming priority from GB 9526706.8 of Dec. 29th 1995.

The novel products of the invention, and the products of the novelprocesses of the invention, all have the advantage of providing IFC wallformation which is more uniform and less prone to premature release ofcore material than when known processes are used for making thecapsules. In particular the IFC polymer is usually deposited almostexclusively on the interface around each droplet, often in ionic orcovalent association with polymeric stabiliser at the interface.

The following are examples of the invention. All parts are by weight.

In the context of this invention proteolytic activity is expressed inKilo NOVO Protease Units (KNPU). The activity is determined relativelyto an enzyme standard (SAVINASE™) and the determination is based on thedigestion of a dimethyl casein (DMC) solution by the proteolytic enzymeat standard conditions, i.e., 50° C., pH 8.3, 9 min. reaction time, 3min. measuring time. A brochure (AF 220/1) providing further details isavailable upon request from Novo Nordisk A/S, Denmark.

EXAMPLE 1

Savinase aqueous preparation supplied by Novo Nordisk A/S havingproteolytic activity of 44 KNPU/g (777 g) is mixed with 45% polyvinylpyrrolidone K60 solution (190 g) and 32.4 g of diethylene triamine(DETA) added to this mixture.

An oil phase is prepared by mixing 221 g of 21% amphipathic emulsionstabiliser with 208 g of a volatile hydrocarbon solvent.

The aqueous enzyme mixture containing the DETA is added to the above oilphase and homogenised with a high shear Silverson mixer to form awater-in-oil emulsion having a mean droplet size of about 3 μm. Thetemperature of the emulsion is kept below 40° C. during this step. Afterformation of the emulsion, an extra 571 g of the volatile solvent isadded to dilute the W/O emulsion.

The resulting emulsion is placed under mechanical stirring and warmed to37° C. An oil-monomer phase is prepared by dissolving 34 g ofterephthaloyl chloride (TPC) in 966 g of the volatile solvent. Thisoil-monomer phase is added to the warm emulsion over 5 minutes toinitiate the wall forming reaction. A polyamide membrane forms aroundthe fine aqueous enzyme droplets. The reaction mixture is left stirringfor 30 minutes to complete the interfacial polymerisation.

The resultant suspension has a dispersed phase which accounted for about33% of the total weight of the suspension.

This suspension is then dehydrated by distillation and subjected to asolvent exchange process with non-ionic surfactant substantially asdescribed in Example 1 of WO 94/25560 to provide a substantially stabledispersion in non-ionic surfactant of particles having a mean size ofabout 3 μm. The suspension has approximately 40 KNPU/g proteolyticactivity.

In this process, shell formation is satisfactory, and a stablemonoparticulate dispersion is formed both initially and after thesolvent exchange and when added to detergent concentrate, when thestabiliser is any of the following copolymers.

A styrene/octadecyl methacrylate/methacrylic acid copolymer in theweight ratio of 30/30/40.

octadecyl methacrylate/methacrylic acid 66/34.

octadecyl methacrylate/methyl methacrylate/acrylic acid 50/25/25.

Octadecyl methacrylate/methacrylic acid 64/36.

Octadecyl methacrylate/methyl methacrylate/acrylic acid/methacrylic acid40/50/5/5.

Acrylonitrile/lauryl acrylate/acrylic acid 25/35/40.

Lauryl methacrylate/styrene/acrylic acid 40/50/10.

Styrene/docosaryl acrylate/methacrylic acid 55/35/10.

Octadecyl methacrylate/vinyl acetate/methyl methacrylate/methacrylicacid 35/10/45/10.

When the process is repeated using a non-ionic block co-polymeravailable under the Trade Name Hypermer 246 the process was not assatisfactory.

EXAMPLE 2 (Comparative)

An aqueous phase is prepared consisting of Savinase Concentrate (aqueousprotease 36 KNPU/g activity polyvinylpyrrolidone aqueous solution (K60,80 parts), diethylenetriamine (13 parts) glacial acetic acid (15 parts)and water (22 parts).

This aqueous phase at pH7 is added with high shear mixing to an oilphase consisting of emulsifier (Span 85; 10 parts) dissolved in avolatile hydrocarbon solvent (280 parts). The resulting 1.85:1water-in-oil emulsion is diluted with more volatile hydrocarbon solvent(240 parts) to 1.0:1.0 W:0.

The pH of the aqueous phase is increased by addition of concentratedsodium hydroxide solution (46%: 10 parts) and milling continued at lessthan 40° C. for 3 minutes. This alkaline emulsion is stirred at 20° C.whilst a solution of the oil phase reactant (terephthaloyl chloride; 13parts) in volatile hydrocarbon solvent (490 parts) is added over 15minutes.

At the end of this reaction period the mixture no longer appears as asmooth water-in-oil emulsion but appears grainy. Under the microscopedroplets of dispersed phase can easily be seen, but there is no apparentwall only gelled polymer attached to the surface showing very poorcapsule formation.

EXAMPLE 3—Preparation of DETA-substituted stabiliser

A solution of an amphipathic polymeric O/W stabiliser (I) (10 parts) ina hydrocarbon solvent (90 parts) is treated with a single addition ofdi-ethylene tri-amine (DETA; 10 parts) at room temperature for 5 minwith vigorous agitation. After this time, some association has occurredbetween the amphipathic polymer and excess DETA (mixture II).

The amphiphatic polymer can be selected from

Octadecyl methacrylate/methyl methacrylate/acrylic acid 50/25/25.

Octadecyl methacrylate/methyl methacrylate/acrylic acid/methacrylic acid40/50/5/5.

Octadecyl methacrylate/vinyl acetate/methyl methacrylate/methacrylicacid 35/10/45/10.

EXAMPLE 4—Preparation of W/O microcapsules with the DETA-substitutedstabiliser as co-reactant

An aqueous solution of the active ingredient (110 parts) is milled intomixture II from Example I (110 parts) to give a W/O emulsion (III)having a mean aqueous droplet size of about 10 micron. Homogenisation isconducted for about 5 minutes.

Separately, a solution is prepared of terephthalic chloride (10 parts)in a hydrocarbon solvent (200 parts). This solution is added to the W/Oemulsion described above with agitation over a period of 5 minutes at25° C. After this time inspection under a visible microscope clearlyshowed the presence of discrete capsules, free of aggregates and clumps.The mean particle size corresponded to the mean particle size of theintermediate W/O emulsion (III).

EXAMPLE 5

The process described in Example 4 was repeated except that the W/Oemulsion (III) is contacted with the terephthalic chloride solution bymeans of an in-line static mixer. This mixing of the two phasescontinued over a period of 15 minutes although the agitation in thein-line mixer only occurred for a few seconds. The effluent from themixer was allowed to collect in a receiving vessel without furthermechanic agitation.

Capsules made in this way were identical in all respects to those fromExample 4 except that experiments to show the strength of the membranefilms implied that the in-line mixing method leads an average to astronger membrane than the batch mixing method.

EXAMPLE 6

This example shows two different ways of encapsulating the enzymewherein the enzyme is precipitated in version B before encapsulation,but not in version A.

Capsules were formed from the following ingredients, in which allamounts are specified in grams. The polymer is a copolymer of 75% byweight acrylamide and 25% acrylic acid, in the form of sodium salt ofmedium (for instance 150,000) molecular weight. Deta is diethylenetriamine. The stabiliser is copolymer of styrene, stearyl methacrylateand acrylic acid. Isopar is a trade name for a volatile hydrocarbon. TPCis terephthalyl chloride.

A B 16.1% Enzyme concentrate 63.38 45.06 Borax 0.63 0.45 29% Polymer9.96 7.08 25% Na2SO4 0.00 21.63 DETA 1.03 0.78 Stabiliser 6.10 4.34Isopar (Batch 1) 34.28 36.05 Isopar (Batch 2) 34.62 34.62 3% TPC inIsopar 43.19 32.52 Activity, KNPU 11.8 8.9

The capsules are made by dissolving the stabiliser in the first batch ofIsopar and then emulsifying the deta into this Isopar with theapplication of homogenisation for 2 minutes using a Silverson (tradename) homogeniser at full speed with cooling in an ice bath for 2minutes.

Separately, the enzyme concentrate, borax, polymer and sodium sulphate(if present), had been prepared as an aqueous enzyme phase. In processA, the solution appeared clear but in process B it appeared cloudy, as aresult of precipitation of the enzyme.

The aqueous enzyme phase is slowly added to the oil phase containingdeta, stabiliser and Isopar, the addition being conducted withemulsification using the Silverson for 10 minutes. The second batch ofIsopar is then added, with emulsification using the Silverson beingconducted for a further 2 minutes and with the water in oil emulsionbeing thermally equilibrated to 20° C. in a water bath.

Accordingly, in this process, the deta has been subjected toemulsification in the presence of a stabiliser for at least 14 minutes.

The solution of TPC is heated to 50° C. and is added quickly withvigorous stirring. The product is stirred for at least 30 minutes whilebeing held at a temperature of 20° C. A suspension of the capsules inIsopar is obtained.

If desired a non-ionic surfactant (Dobanol 25-7) can be added and theIsopar then distilled off to produce a dispersion in the surfactant.Alternatively the dispersion in Isopar can be used.

The enzymatic storage stability of encapsulated protease A and B, andliquid lipase in presence of the protease capsules has been determinedin a commercially available US liquid detergent (WISK Free Clear), wherepH was adjusted to 10.1.

Formulations:

I: 2% Savinase 4.8 L, 1% Lipolase 100 L, 97% US liquid detergent

II: 1% savinase capsules A, 1% Lipolase 100 L, 98% US liquid detergent

III: 1% Savinase capsules B, 1% Lipolase 100 L, 98% US liquid detergent

IV: 1% Lipolase 100 L, 99% US liquid detergent.

Formulations I to IV were left at 30° C. for 0, 4 and 8 days, and theresidual protease and lipase activities were measured:

Savinase stability, % residual activity:

Formulation 0 4 8 days I 100 87.2 79.1 II 100 82.9 67.6 III 100 97.491.4

The storage stability of protease capsules A, formulation II (withoutsulfate) is poorer than that of liquid protease (due to the increasedconcentration of active protease inside the capsules). Precipitating theprotease with sulfate (capsules B, formulation III) significantlyimproves the storage stability compared to both capsules A and liquidprotease.

Lipolase stability, % residual activity:

Formulation 0 4 8 days I 100 8.9 — II 100 70.2 46.1 III 100 92.6 89.1 IV100 92.3 90.2

The storage stability of lipase is significantly improved whenprecipitating the protease with sulfate. However, compared to othersystems, the storage stability of the non-precipitated composition (A)was also satisfactory.

Improved results are obtained when the polymer is replaced by the use ofsodium polyacrylate homopolymer of similar molecular weight and,especially, when the stabiliser is replaced by a copolymer of styrene,stearyl methacrylate and maleic anhydride.

EXAMPLE 7

This example shows the production of immobilised enzyme, and inparticular immobilised amyloglucosidase (AMG). The resultant particlesare useful as encapsulated enzyme for industrial use since they allowthe reactants and the products from the reaction to diffuse through thewall of the capsules but do not allow the enzyme itself to diffuse out.

4.37 grams deta is emulsified into 10.4 grams of a 30% solution of apolymeric stabiliser (as in the preceding example) and 114 grams Isoparusing a Silverson homogeniser at full speed for 2 minutes with coolingon an ice bath. 120 grams of an 18.4% enzyme concentrate (188 AGU/g) isslowly added with further emulsification for 10 minutes. 187 grams of 3%solution in Isopar of terephthalyl chloride at 50° C. is then quicklyadded and emulsification is continued for 5 minutes. The emulsion isleft stirring at 20° C. for 30 minutes. 170 grams Dobanol 25-7 is thenadded and the water and Isopar are distilled off under vacuum (up to 95°C. at 20 mbar).

In order to test the performance of the products, the following buffersand sample preparations and tests were conducted.

Buffers:

Buffer A: 0.1 M Acetate, pH 4.3

Buffer B: 0.1 M Borax, pH not adjusted

Substrate: 0.1% p-Nitrophenyl-alpha-D-glucopyranoside (NBS Biologicals)in Buffer A

Sample Preparation:

I) 0.774 g AMG capsules+1.624 g Dobanol 25-7+47.61 g Buffer

II) 0.271 g AMG concentrate+1.968 g Dobanol 25-7+47.78 g Buffer A

III) 1.507 g Dobanol 25.7+48.52 g Buffer A

The samples (with an enzyme activity of 1.0 AGU/g) were vigorouslystirred for one hour.

The following samples were prepared:

IV) 2 ml I+4 ml Substrate

V) 2 ml I filtrate through a 0.45 micron filter (Millipore)+4 mlSubstrate

VI) 2 ml II+4 ml Substrate

Blind) 2 ml III+4 ml Substrate.

Filtration through a 0.45 micron filter removes all capsules.

Samples IV to VI and Blind were left stirring at 25° C. for one hour, 6ml buffer B was added and the samples were left stirring forapproximately five minutes and filtered through a 0.2 micron filter. Theabsorbance at 400 nm was measured.

The reaction between the substrate and the enzyme produced glucose andp-nitrophenol gives a yellow liquid under alkaline conditions, which isobtained with Buffer B. The produced colour is proportional to the AMGconcentration. The colis is measured with a spectrophotometer at 400 nm(OD400).

Results:

Sample Absorbence at 400 nm IV: 0.644 V: 0.011 VI: 0.762 Blind: 0.005

The leakage of enzyme from the capsules (sample V) is approximately:

100.(0.011−0.005)/(0.762−0.005)˜1%

The efficiency of the encapsulated enzyme (sample IV) on the substrateis approximately:

100.(0.644−0.005)/(0.762−0.005)˜84%

The capsules is thus only leaking very small amounts of the enzyme, butthe enzyme is nearly as efficient on the substrate as not encapsulatedenzyme.

What is claimed is:
 1. A particulate composition comprising particleshaving a hydrophilic core within a shell comprising a membranecomprising an association product of (a) an interfacial condensationproduct formed by reaction between an oil soluble first IFC reactanthaving at least two first condensation groups and a water soluble secondIFC reactant having at least two second condensation groups and (b) anoil soluble or oil swellable amphipathic polymeric stabiliser which willconcentrate at the interface between oil and water and which hasrecurring hydrophobic groups and recurring reactive hydrophilic groupswhich associate with the second condensation groups.
 2. A compositionaccording to claim 1 in which the association comprises a condensationreaction.
 3. A composition according to claim 1 or claim 2 in which thestabiliser comprises carboxylic groups and the second IFC reactant is anamine.
 4. A composition according to claim 1 in which the stabiliser isa copolymer of monomers comprising ethylenically unsaturateddicarboxylic acid and the second IFC reactant is an amine.
 5. Acomposition according to claim 1 in which the stabiliser is a randomcopolymer formed by copolymerisation of a blend of hydrophilic andhydrophobic monomers.
 6. A composition according to claim 1 in which thestabiliser is a random copolymer of a blend of hydrophobic monomersselected from styrene and alkyl (meth) acrylates and hydrophilicmonomers comprising ethylenically unsaturated polycarboxylic acid andthe second reactant is diethylene triamine or other aliphatic polyamine.7. A composition according to claim 1 in which the core comprisespolymeric material.
 8. A composition according to claim 1 in which thecore comprises active ingredient selected from pharmaceutical activeingredients, agricultural active ingredients, optical bleaches, photobleaches, proteins, fragrances, inks, and enzymes.
 9. A compositionaccording to claim 1 in the form of a dispersion in a water immiscibleliquid or in a water miscible liquid of the particles and wherein theparticles have a size at least 95% by weight below 30 μm.
 10. Acomposition according to claim 1, in the form of a dispersion in anaqueous liquid of said particles.
 11. A composition according to claim10, wherein said aqueous liquid is an aqueous surfactant.